//
// Created by zhangrongxiang on 2018/2/23 17:02
// File sqlite
//

#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>

typedef struct InputBuffer_t InputBuffer;

enum ExecuteResult_t {
    EXECUTE_SUCCESS, EXECUTE_TABLE_FULL
};
typedef enum ExecuteResult_t ExecuteResult;

enum MetaCommandResult_t {
    META_COMMAND_SUCCESS,
    META_COMMAND_UNRECOGNIZED_COMMAND
};
typedef enum MetaCommandResult_t MetaCommandResult;

enum PrepareResult_t {
    PREPARE_SUCCESS,
    PREPARE_SYNTAX_ERROR,
    PREPARE_UNRECOGNIZED_STATEMENT
};
typedef enum PrepareResult_t PrepareResult;

enum StatementType_t {
    STATEMENT_INSERT, STATEMENT_SELECT
};
typedef enum StatementType_t StatementType;

//const uint32_t COLUMN_USERNAME_SIZE = 32;
//const uint32_t COLUMN_EMAIL_SIZE = 255;
#define COLUMN_USERNAME_SIZE 32
#define COLUMN_EMAIL_SIZE 255
struct Row_t {
    uint32_t id;
    char username[COLUMN_USERNAME_SIZE];
    char email[COLUMN_EMAIL_SIZE];
};
typedef struct Row_t Row;

#define size_of_attribute(Struct, Attribute) sizeof(((Struct*)0)->Attribute)

//const uint32_t ID_SIZE = size_of_attribute(Row, id);
//const uint32_t USERNAME_SIZE = size_of_attribute(Row, username);
//const uint32_t EMAIL_SIZE = size_of_attribute(Row, email);
//const uint32_t ID_OFFSET = 0;
//const uint32_t USERNAME_OFFSET = ID_OFFSET + ID_SIZE;
//const uint32_t EMAIL_OFFSET = USERNAME_OFFSET + USERNAME_SIZE;
//const uint32_t ROW_SIZE = ID_SIZE + USERNAME_SIZE + EMAIL_SIZE;
//
//const uint32_t PAGE_SIZE = 4096;
//const uint32_t TABLE_MAX_PAGES = 100;
//const uint32_t ROWS_PER_PAGE = PAGE_SIZE / ROW_SIZE;
//const uint32_t TABLE_MAX_ROWS = ROWS_PER_PAGE * TABLE_MAX_PAGES;
/////////////////////////////////////////////////////////////////////////////////////

#define ID_SIZE  size_of_attribute(Row, id)
#define USERNAME_SIZE  size_of_attribute(Row, username)
#define EMAIL_SIZE  size_of_attribute(Row, email)
#define ID_OFFSET  0
#define USERNAME_OFFSET  (ID_OFFSET + ID_SIZE)
#define EMAIL_OFFSET  (USERNAME_OFFSET + USERNAME_SIZE)
#define ROW_SIZE  (ID_SIZE + USERNAME_SIZE + EMAIL_SIZE)

#define PAGE_SIZE  4096
#define TABLE_MAX_PAGES  100
#define ROWS_PER_PAGE  (PAGE_SIZE / ROW_SIZE)
#define TABLE_MAX_ROWS  (ROWS_PER_PAGE * TABLE_MAX_PAGES)

struct Table_t {
    void **pages[TABLE_MAX_PAGES];
    uint32_t num_rows;
};
typedef struct Table_t Table;

void print_row(Row *row) {
    printf("(%d, %s, %s)\n", row->id, row->username, row->email);
}

void serialize_row(Row *source, void *destination) {
    memcpy(destination + ID_OFFSET, &(source->id), ID_SIZE);
    memcpy(destination + USERNAME_OFFSET, &(source->username), USERNAME_SIZE);
    memcpy(destination + EMAIL_OFFSET, &(source->email), EMAIL_SIZE);
}

void deserialize_row(void *source, Row *destination) {
    memcpy(&(destination->id), source + ID_OFFSET, ID_SIZE);
    memcpy(&(destination->username), source + USERNAME_OFFSET, USERNAME_SIZE);
    memcpy(&(destination->email), source + EMAIL_OFFSET, EMAIL_SIZE);
}

void *row_slot(Table *table, uint32_t row_num) {
    uint32_t page_num = row_num / ROWS_PER_PAGE;
    void *page = table->pages[page_num];
    if (!page) {
        // Allocate memory only when we try to access page
        page = table->pages[page_num] = malloc(PAGE_SIZE);
    }
    uint32_t row_offset = row_num % ROWS_PER_PAGE;
    uint32_t byte_offset = row_offset * ROW_SIZE;
    return page + byte_offset;
}

Table *new_table() {
    Table *table = malloc(sizeof(Table));
    table->num_rows = 0;

    return table;
}

struct InputBuffer_t {
    char *buffer;
    size_t buffer_length;
    ssize_t input_length;
};

MetaCommandResult do_meta_command(InputBuffer *input_buffer) {
    if (strcmp(input_buffer->buffer, ".exit") == 0) {
        exit(EXIT_SUCCESS);
    } else {
        return META_COMMAND_UNRECOGNIZED_COMMAND;
    }
}


struct Statement_t {
    StatementType type;
    Row row_to_insert;  // only used by insert statement
};
typedef struct Statement_t Statement;

PrepareResult prepare_statement(InputBuffer *input_buffer,
                                Statement *statement) {
    if (strncmp(input_buffer->buffer, "insert", 6) == 0) {
        statement->type = STATEMENT_INSERT;
        int args_assigned = sscanf(
                input_buffer->buffer, "insert %d %s %s", &(statement->row_to_insert.id),
                statement->row_to_insert.username, statement->row_to_insert.email);
        if (args_assigned < 3) {
            return PREPARE_SYNTAX_ERROR;
        }
        return PREPARE_SUCCESS;
    }
    if (strcmp(input_buffer->buffer, "select") == 0) {
        statement->type = STATEMENT_SELECT;
        return PREPARE_SUCCESS;
    }

    return PREPARE_UNRECOGNIZED_STATEMENT;
}

InputBuffer *new_input_buffer() {
    InputBuffer *input_buffer = malloc(sizeof(InputBuffer));
    input_buffer->buffer = NULL;
    input_buffer->buffer_length = 0;
    input_buffer->input_length = 0;

    return input_buffer;
}

ExecuteResult execute_insert(Statement *statement, Table *table) {
    if (table->num_rows >= TABLE_MAX_ROWS) {
        return EXECUTE_TABLE_FULL;
    }

    Row *row_to_insert = &(statement->row_to_insert);

    serialize_row(row_to_insert, row_slot(table, table->num_rows));
    table->num_rows += 1;

    return EXECUTE_SUCCESS;
}

ExecuteResult execute_select(Statement *statement, Table *table) {
    Row row;
    uint32_t i = 0;
    for (; i < table->num_rows; i++) {
        deserialize_row(row_slot(table, i), &row);
        print_row(&row);
    }
    return EXECUTE_SUCCESS;
}

ExecuteResult execute_statement(Statement *statement, Table *table) {
    switch (statement->type) {
        case (STATEMENT_INSERT):
            return execute_insert(statement, table);
        case (STATEMENT_SELECT):
            return execute_select(statement, table);
    }
}

void print_prompt(int count) {
    printf("db %3d> ", count);
}

void read_input(InputBuffer *input_buffer) {
    ssize_t bytes_read =
            getline(&(input_buffer->buffer), &(input_buffer->buffer_length), stdin);

    if (bytes_read <= 0) {
        printf("Error reading input\n");
        exit(EXIT_FAILURE);
    }

    // Ignore trailing newline
    input_buffer->input_length = bytes_read - 1;
    input_buffer->buffer[bytes_read - 1] = 0;
}

int main(int argc, char *argv[]) {
    int count;
    Table *table = new_table();
    InputBuffer *input_buffer = new_input_buffer();
    while (count++ < 10000) {
        print_prompt(count);
        read_input(input_buffer);

        if (input_buffer->buffer[0] == '.') {
            switch (do_meta_command(input_buffer)) {
                case (META_COMMAND_SUCCESS):
                    continue;
                case (META_COMMAND_UNRECOGNIZED_COMMAND):
                    printf("Unrecognized command '%s'\n", input_buffer->buffer);
                    continue;
            }
        }

        Statement statement;
        switch (prepare_statement(input_buffer, &statement)) {
            case (PREPARE_SUCCESS):
                break;
            case (PREPARE_UNRECOGNIZED_STATEMENT):
                printf("Unrecognized keyword at start of '%s'.\n",
                       input_buffer->buffer);
                continue;
            default:
                break;
        }
        switch (execute_statement(&statement, table)) {
            case (EXECUTE_SUCCESS):
                printf("Executed.\n");
                break;
            case (EXECUTE_TABLE_FULL):
                printf("Error: Table full.\n");
                break;
        }
    }
}
